Systems and methods for repairing bone with multiple tools

ABSTRACT

A method for repairing a bone of a patient may include superimposing a first virtual boundary on a virtual bone and superimposing a second virtual boundary on the virtual bone. The method may further include robotically modifying the bone of the patient with a planar tool along a first working boundary to create a first surface. The first working boundary may correspond to the first virtual boundary. The method may further include robotically modifying the bone of the patient with a rotary tool along a second working boundary to create a second surface. The second working boundary may correspond to the second virtual boundary.

CROSS-REFERENCE TO RELATED APPLICATION(S)

This application is a continuation of pending U.S. application Ser. No.14/600,972, filed on Jan. 20, 2015, which is incorporated herein byreference in its entirety.

TECHNICAL FIELD

Embodiments of the present disclosure relate generally to medicalprocedures, and more particularly, to methods and systems for planningand performing bone repair procedures.

BACKGROUND

Robotic surgical systems are currently used to perform bone repairprocedures, such as partial knee replacement surgeries. These proceduresmay be performed using a robotic device having a single tool. After thebone has been prepared, an implant component may be cemented onto theprepared bone. Any deviations between the prepared bone surface and thebone-contacting surface of the implant may be filled with cement.However, to receive a press-fit implant component (e.g., withoutcement), the bone surfaces must be precisely shaped to receive, andsometimes match, the bone-contacting surfaces of the component. Currentmethods and tools used to prepare bone may not result in prepared bonesurfaces that correspond to the implant surfaces with enough precisionto hold a press-fit implant. More precise bone preparation may alsoimprove the fixation of cemented implant components.

SUMMARY

Embodiments of the present disclosure relate to, among other things,methods and systems for planning and performing bone repair procedures.Each of the embodiments disclosed herein may include one or more of thefeatures described in connection with any of the other disclosedembodiments.

A method for repairing a bone of a patient may include superimposing afirst virtual boundary on a virtual bone; superimposing a second virtualboundary on the virtual bone; robotically modifying the bone of thepatient with a planar tool along a first working boundary to create afirst surface, wherein the first working boundary corresponds to thefirst virtual boundary; and robotically modifying the bone of thepatient with a rotary tool along a second working boundary to create asecond surface, wherein the second working boundary corresponds to thesecond virtual boundary.

The method may additionally or alternatively include one or more of thefollowing features or steps: the bone may be a tibia, the first surfacemay be a tibial floor, and the second surface may be a tibial wall; atleast a portion of the tibial wall may be substantially perpendicular toat least a portion of the tibial floor; the first surface may be planar;the planar tool and the rotary tool may be adapted to removably connectto the end of a robotic arm; the method may further include at least oneof (a) removing the planar tool from the end of the robotic arm andconnecting the rotary tool to the end of the robotic arm, or (b)removing the rotary tool from the end of the robotic arm and connectingthe planar tool to the end of the robotic arm; the method may furtherinclude securing an implant to the first surface without the use of anadhesive; the implant may be at least partially formed of a porousmaterial; the implant may include a keel; the method may furtherinclude, before securing the implant and after creating the firstsurface, robotically modifying the first surface with a drill to createan indentation in the first surface to receive the keel of the implant;the drill may include a first drilling portion having a first diameterand a second drilling portion having a second diameter larger than thefirst diameter; the planar tool, rotary tool, and drill may each beadapted to removably connect to an end of a robotic arm; the method mayfurther include removing at least one of the planar tool or the rotarytool from the end of the robotic arm and connecting the drill to the endof the robotic arm; the method may further include placing an implantadjacent to the first and second surfaces of the bone; the implant mayinclude a distal planar surface at least partially formed of a porousmaterial, and the step of placing the implant may be carried out withoutuse of an adhesive; the distal planar surface of the implant may be insubstantially continuous contact with the first surface of the bone; thebone may be a femur, and the method may further include securing apress-fit component to the femur; and the planar tool may be a saw, therotary tool may be a burr, and the saw and the burr may be adapted tointerchangeably connect to the end of a robotic arm.

In another embodiment, a method for bone preparation may includesuperimposing a first virtual boundary on a virtual bone; andsuperimposing a second virtual boundary on the virtual bone, wherein aplanar surface of the second virtual boundary may be offset from andsubstantially parallel to a planar surface of the first virtualboundary.

The method may additionally or alternatively include one or more of thefollowing features or steps: the virtual bone may represent a tibia; theplanar surface of the first virtual boundary may be configured to guidea robotic arm to cut a bone with a first tool to create a first surface;the planar surface of the second virtual boundary may be configured toguide the robotic arm to extend the first surface of the bone with asecond tool; and the second virtual boundary may be offset in a superiordirection with respect to the first virtual boundary.

In yet another embodiment, a computer system for controlling a medicalrobotic system for preparing a bone of a patient may include anelectronic storage device storing instructions for controlling themedical robotic system; and a processor configured to execute theinstructions to: determine a first virtual boundary for a first toolbased on received patient parameters; determine a second virtualboundary for a second tool based on the received patient parameters,wherein the first tool is different than the second tool; and constrainmotion of the medical robotic system based on the first virtual boundaryand the second virtual boundary.

The computer system may additionally or alternatively include one ormore of the following features: the processor may be further configuredto execute instructions to position and align, in six degrees offreedom, at least one of the first or second tools; constraining motionof the medical robotic system may include constraining motion of thefirst tool and constraining motion of the second tool; and the processormay be further configured to execute instructions to: determine a thirdvirtual boundary for a third tool based on the received patientparameters, wherein the third tool is different than the first andsecond tools, and constrain motion of the third tool based on the thirdvirtual boundary.

It may be understood that both the foregoing general description and thefollowing detailed description are exemplary and explanatory only andare not restrictive of the invention, as claimed.

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawings, which are incorporated in and constitute apart of this specification, illustrate exemplary embodiments of thepresent disclosure and together with the description serve to explainthe principles of the disclosure.

FIG. 1 illustrates a surgical system, according to an exemplaryembodiment.

FIG. 2 illustrates a planar tool attachment, according to an exemplaryembodiment.

FIG. 3 illustrates a burr attachment, according to an exemplaryembodiment.

FIG. 4 illustrates a drill attachment, according to an exemplaryembodiment.

FIG. 5 illustrates femoral and tibial components of an implant system,according to an exemplary embodiment.

FIG. 6 illustrates an inferior perspective view of the tibial component,according to an exemplary embodiment.

FIG. 7 illustrates a guidance module monitor showing an image of a firstvirtual volume, according to an exemplary embodiment.

FIG. 8 illustrates working boundaries corresponding to the first virtualvolume shown in FIG. 7, according to an exemplary embodiment.

FIG. 9 illustrates a guidance module monitor showing an image of asecond virtual volume, according to an exemplary embodiment.

FIG. 10 illustrates working boundaries corresponding to the secondvirtual volume shown in FIG. 10, according to an exemplary embodiment.

FIG. 11 illustrates the first and second virtual volumes superimposed ona virtual bone, according to an exemplary embodiment.

FIG. 12 is a method flow chart illustrating an exemplary method forrepairing a bone.

FIG. 13 illustrates a tibial component that has been implanted on thesuperior surface of a tibial condyle, according to an exemplaryembodiment.

DETAILED DESCRIPTION

Overview

The present disclosure is drawn to methods and systems for planning andperforming bone repair procedures. The methods disclosed in thisapplication may be performed using a robotic surgical device and mayallow a practitioner to plan for or perform bone repair procedures usingmultiple tools. During the disclosed procedures, use of different toolsmay allow the prepared bone surfaces to match the shape of thebone-contacting surfaces of implant components.

When referring to specific directions with respect to a human body, theterm “proximal” means closer to the heart and the term “distal” meansmore distant from the heart. The term “inferior” means toward the feetand the term “superior” means toward the head. The term “anterior” meanstoward the front of the body or the face and the term “posterior” meanstoward the back of the body. The term “medial” means toward the midlineof the body and the term “lateral” means away from the midline of thebody. When directions are used with respect to a user of a device,“proximal” means closer to the user and “distal” means farther away fromthe user.

EXEMPLARY EMBODIMENTS

Surgical System Overview

Referring to FIG. 1, according to an exemplary embodiment, a surgicalsystem 10 may include a robotic device 12, a navigation system 22, and aguidance module 38. In general, a medical practitioner, such as asurgeon, may use the robotic device 12 to perform bone repair proceduresas described in this application. The navigation system 22 may track thepatient's bone, as well as the robotic device 12, to allow the surgeonto visualize the bone and tools on one or more displays 26, 44 during aprocedure. The guidance module 38 provides an interface for a user to,for example, receive output from the surgical system in the form ofinstructions and other guidance, and to provide input to the system,such as modifications or adjustments to a bone repair plan. The guidancemodule 38 may house a computer 46, including the hardware and softwarerequired for execution of the processes described in this disclosure.The robotic device 12, the navigation system 22, and the guidance module38 may all be in communication with each other via wired or wirelessconnections in order to guide the robotic device 12 during a procedure.

The robotic device 12 may include a base 14, an arm 16, and a toolsystem 17. The base 14 may support the arm 16 and may be positionablenear the patient. The arm 16 may include several links, and may bemovable by the user to position and orient the tool system 17. The toolsystem 17 may include a tool body 18 and a tool attachment 20. The toolbody 18 may be located at a distal end of the arm 16. In one embodiment,the tool body 18, via the arm 16, may be positioned and oriented in sixdegrees of freedom. In an alternative embodiment, the tool body 18 maybe positioned and oriented in more than six degrees of freedom. The toolbody 18 may couple to the tool attachment 20, which is the portion ofthe tool system 17 that modifies bone. As shown in FIGS. 1 and 2, thetool attachment 20 may be a planar cutting tool such as a saw 48.However, as will be described in greater detail below, multiple types oftool attachments 20 may be interchangeably coupled to the tool body 18.

The navigation system 22 may include a stand 24, a monitor 26, adetection device 28, and one or more trackable elements 30, 32, 34, 36.The stand 24 may support the monitor 26 and detection device 28 and maybe positionable in the operating room. The monitor 26 may display imagesthat allow medical practitioners to view a surgical plan or the progressof a procedure. The detection device 28 may include one or moredetectors that are used to detect the location of the trackable elements30, 32, 34, 36, which are fixed securely to tracked objects. Forexample, trackable element 30 may be fixed to the base 14 of the roboticdevice 12, trackable element 32 may be fixed to the tool system 17,trackable element 34 may be fixed to a first bone of a patient (e.g., atibia 6), and trackable element 36 may be fixed to a second bone of apatient (e.g., a femur 8).

The navigation system 22 may be any type of navigation system configuredto track the pose (i.e., position and orientation) of a bone. Forexample, the navigation system 22 may be a non-mechanical trackingsystem, a mechanical tracking system, or any combination ofnon-mechanical and mechanical systems.

In one embodiment, referring to FIG. 1, the navigation system 22 may bea non-mechanical tracking system such as an optical tracking system. Inone example of an optical tracking system, the detection device 28 maydetect visible light and may be, for example, a MicronTracker (ClaronTechnology Inc., Toronto, Canada). In an additional or alternativeexample, the detection device 28 may include a stereo camera pairsensitive to infrared radiation.

The trackable elements 30, 32, 34, 36 may be configured to be “visible”by the type of detection device 28 being used. Depending on thedetection device 28, the trackable elements may be active (e.g.,light-emitting diodes or LEDs) or passive (e.g., reflective spheres, acheckerboard pattern, etc.) and have a unique geometry (e.g., a uniquegeometric arrangement of the markers) or, in the case of active markers,a unique firing pattern.

In operation, the detection device 28 detects positions of the trackableelements 30, 32, 34, 36, and the surgical system 10 (e.g., the computersystem 46, which may include embedded electronics associated with thedetection device 28) calculates a pose of the tracked objects, to whichthe trackable elements are fixed, based on the trackable elements'positions, unique geometry, and known geometric relationship to thetracked object.

The guidance module 38 may include a stand 40, an input device 42, amonitor 44, and a computer system 46. The stand 40 may support the inputdevice 42, monitor 44, and computer system 46. The input device 42 maybe a keyboard, mouse, or any other interface that allows the user toprovide information to the surgical system 10. In an additional oralternative embodiment, the monitor 44 may include a touch screen thatserves as the input device. Similar to monitor 26, the monitor 44 maydisplay images that allow medical practitioners to view a surgical planor the progress of a surgical procedure.

The computer system 46 may include a processor and an electronic storagedevice. The components of the computer 46 may be housed anywhere withinsurgical system 10. Additionally or alternatively, all or portions ofthe computer 46 may be housed in a remote location. The processor can beimplemented as a general purpose processor, an application specificintegrated circuit (ASIC), one or more field programmable gate arrays(FPGAs), a group of processing components, or other suitable electronicprocessing components. The electronic storage device (e.g., memory,memory unit, etc.) may be one or more devices (e.g., RAM, ROM, Flashmemory, hard disk storage, etc.) for storing data and/or computer codefor completing or facilitating the various processes and functionsdescribed in the present application. The electronic storage device maybe or include volatile memory or non-volatile memory. The electronicstorage device may include database components, object code components,script components, or any other type of information structure forsupporting the various activities described in the present application.In one embodiment, the electronic storage device is communicablyconnected to the processor via the computer 46 and includes computercode for executing (e.g., by the processor) one or more processesdescribed herein.

Tool System

As noted above, the tool system 17 may include a tool body 18 and a toolattachment 20. The tool body 18 may be interchangeably coupled to avariety of tool attachments 20 that may be used during the proceduresdescribed herein. Each of the tool attachments 20 may be connected to,removed from, or reconnected to the end of the tool body 18, and thusthe end of the robotic arm 16, during a surgical procedure. Referring toFIGS. 2-4, for example, the tool attachment 20 may be a planar tool,such as a saw 48, or a rotary tool, such as a burr 50 or a drill 52.

Referring to FIG. 2, in one embodiment, the saw 48 may be an oscillatingsaw with a cutting surface on its distal end. During operation, the saw48 may oscillate around an axis, such as an axis perpendicular to theplane of the blade 48 (e.g., in FIG. 2, the saw 48 may oscillate in andout of the page). In other embodiments, the saw 48 may oscillate aroundan axis that is oriented differently with respect to the tool body 18 orportions of the saw 48. Although saw 48 is shown as straight, saw 48 mayalternatively be bent, changing the angle of the cutting surface. Theoscillating saw may be a sagittal saw. In another embodiment, the planartool may be a reciprocating saw (e.g., a blade or a rasp). Reciprocatingsaws may have a cutting surface along a longitudinal edge (e.g., ablade) or may have a planar surface with teeth (e.g., a rasp). In someembodiments, the planar tool may be a wire saw.

Referring to FIG. 3, the burr 50 may have a portion at its distal endthat rotates around a longitudinal axis and may be operated to removetissue or bone. The distal tip of the burr 50 may be curved, flattened,oval, irregularly-shaped, or any other shape. Referring to FIG. 4, thedrill 52 may also rotate around a longitudinal axis and may be operatedto remove tissue or bone. In one embodiment, the drill 52 includes afirst drilling portion 53 having a first diameter and a second drillingportion 55 having a second diameter larger than the first diameter. Adrill having more than one diameter may be beneficial when preparingbone to receive different portions of implant components.

The tool attachment 20 may be any other type of rotary tool, such as arouter. In yet another embodiment, the tool attachment 20 may be awaterjet used to remove tissue or for irrigation. The tool attachment20, however, may be any type of tool used to modify or remove tissue orbone. Modifications may include cutting, carving, sculpting, filing,grinding, drilling, deforming, or any other way of modifying tissue orbone consistent with the type of tool attachment 20 and the motion ofthe tool attachment 20.

The tool body 18 may include a connection member 54, which may beconfigured to receive different adaptors 58, 60, 62. The adaptors 58,60, 62 allow their corresponding attachments 48, 50, 52 to be coupled toand controlled by the tool body 18. For example, when connected to thetool body 18, the adaptor 58 may include a mechanism to allow the saw 20to oscillate around a vertical axis through the adaptor 58. In contrast,the adaptors 60, 62 for rotary cutting tools may allow the burr 50 anddrill 52, respectively, to rotate around a longitudinal axis through theadaptors 60, 62.

Implant System

FIG. 5 illustrates an implant system 54 that may be implanted using theprocedures described in this application. The implant system 54 mayinclude a femoral component 56 and a tibial component 72, referred togenerally as “implant components.” FIG. 6 illustrates an inferiorperspective view of the tibial component 72. The femoral component 56may be implanted on a distal end of a femur and may be designed toreplace the articular surface of a femoral condyle, and the tibialcomponent 72 may be implanted on a proximal end of a tibia and may bedesigned to replace the articular surface of a tibial condyle.

The femoral component 56 may include a femoral base 58 and a femoralarticular portion 60. When implanted, the femoral base 58 may be fixedto the femur, and the femoral articular portion 60 may be fixed to thefemoral base 58. The bone-contacting surface of the femoral base 58 mayinclude a substantially planar surface 64 and a curved surface 61. Inthe embodiment shown in FIG. 5, the substantially planar surface 64 maycontact a posterior surface of the femur. The femoral articular portion60 may include a curved articular surface 70, which may contact thecorresponding articular surface 76 of the tibial component 72.

The femoral component 56 may further include a first post 66 and asecond post 68 protruding proximally from the femoral base 58. In oneembodiment, the first post 66 is an anterior post, and the second post68 is a posterior post. The posts 66, 68 may be frustrums, cylindrical,or any other elongated shape protruding from the articular surface ofthe femoral component 56. In one embodiment, the posts 66, 68 mayinclude elongated ridges (not shown) extending in the proximal-distaldirection along the outer surface of posts 66, 68.

The tibial component 72 may include a tibial base 74 and a tibialarticular portion 76. When implanted, the tibial base 74 may be fixed tothe tibia and the tibial articular portion 76 may be fixed to the tibialbase 74. The tibial component 72 may be generally D-shaped and include afirst side wall 78 and a second side wall 80. The first side wall 78 maybe substantially planar, and the second side wall 80 may be curved. Thetibial articular portion 76 may include an articular surface 82. In oneembodiment, the articular surface 82 may be concave. In an alternativeembodiment, the articular surface 82 may be planar.

As shown in FIG. 6, the bone-contacting surface of the tibial base 74may include an inferior surface 84 and one or more elongated keels 86,88 protruding from the surface 84. The inferior surface 84 may beplanar. The keel 86 may extend in an anterior-posterior direction, andthe keel 88 may extend in a medial-lateral direction. In one embodiment,the keels 86, 88 are generally perpendicular to each other.

The keels 86, 88 may have one or more extensions 92. The extensions 92may extend laterally from the main body portions of keels 86, 88. Forexample, in FIG. 6, extension 92 may extend in an anterior-posteriordirection from the main body 90 of keel 88. The extensions 92 may bewedge-shaped and may taper to become more narrow as they extend distallyfrom the inferior surface 84. The extensions 92 may be the same heightas the keels 86, 88.

The keels 86, 88 may additionally or alternatively have one or more fins93. The fins 93, like the extensions 92, may protrude from the main bodyof the keels 86, 88. The fins 93 also may be wedge-shaped, and they maytaper to a narrow point as they extend distally from the inferiorsurface 84. In one embodiment, the fins 93 are about half of the heightof the keels 86, 88. The tibial base 74 may further include an aperture94 through which another device, instrument, or material (e.g., a bonescrew) can be inserted to, for example, help secure the tibial base 74to the tibia 6.

The femoral component 56 and the tibial component 72 may be constructedfrom any combination of solid metal, porous metal, polymers, or othermaterials. The femoral base 58 and the tibial base 74 may be made of ametal such as titanium or stainless steel. In one embodiment, thefemoral and tibial bases 58, 74 are made of a porous metal designed tofacilitate bone ingrowth, as described in U.S. patent application Ser.No. 14/212,051, filed Mar. 14, 2014, titled “Unicondylar Tibial KneeImplant,” and incorporated by reference herein in its entirety. Thefemoral and tibial articular portions 60, 76 may be made of a polymermaterial such as PEEK. In some embodiments, portions of the implantcomponents, such as the femoral or tibial bases 58, 74, may include morethan one type of material. For example, portions of femoral and tibialbases 58, 74 may be made of a porous material while other portions aremade of non-porous material.

In some embodiments, the implant system 54 may include only the tibialcomponent 72 or only the femoral component 56, or may include both thefemoral component 56, the tibial component 72, and a patella-femoralcomponent for implantation on the anterior surface of the femur.Although a medial left tibial component 72 and femoral component 56 areillustrated in the drawings, the implant system 54 may include anysubset and combination of the following implant components: 1) medialleft tibial component; 2) medial left femoral component; 3) lateral lefttibial component; 4) lateral left femoral component; 5) medial righttibial component; 6) medial right femoral component; 7) lateral righttibial component; 8) lateral right femoral component; and 8)patella-femoral component on the anterior surface of the femur. Thevarious implant components may be designed to accommodate the differentanatomy of the left and right leg bones and the medial and lateralarticular surfaces of each bone.

In other embodiments, the implant system 54 may include implantcomponents for other bones or joints. For example, the implantcomponents may be for implantation on a patient's acetabulum or anyother bone, including bones in the ankle, shoulder, or spine. Theimplant components may be for use in a joint or outside of a joint. Forexample, the implant components may be a plate and screws to repair abone fracture. The methods described herein may be used to prepare boneto receive implants of different shapes and having differentbone-contacting surfaces.

The preparation of the bone to accept implant components of the implantsystem 54 may be facilitated by the various devices and methodsdescribed in this application. In general, once the bone is prepared, animplant component may be secured to the bone. In one embodiment, one ormore implant components are secured to bone using methyl methacrylate,generally termed bone cement. In other embodiments, implant componentsmay be secured to the bone directly, i.e., without bone cement. Fixationof an implant component to the bone without bone cement may be calledcementless fixation or press-fit fixation.

Guidance Using Virtual Boundaries

The surgical system 10, including the navigation system 22, the computersystem 46, and the robotic device 12, may be used to guide a medicalpractitioner during a surgical procedure. Guided bone modifications maybe implemented using the above-described tool system and may preparebone for receiving the above-described implant components.

Prior to the surgical procedure, the patient's anatomy (e.g., tibia andfemur) may be scanned using any known imaging technique, such as CT orMRI. The scan data may then be segmented to obtain a three-dimensionalrepresentation of the patient's anatomy. The images of the patient'sanatomy may be used during pre-operational planning to determineapproximate placement of the implant components.

Once the patient is in the operating room, the navigation system 22 maybe used to determine the pose (i.e., position and orientation) of thepatient's anatomy relative to the detection device 28. To determine thepose of the tibia and femur, for example, trackable elements 34, 36 areattached to those bones. Any known registration process may then be usedto register the physical anatomy (e.g., the tibia and femur) to thevirtual representation of the anatomy created beforehand (e.g. thepreoperative three-dimensional representation). Registration is theprocess of correlating two coordinate systems, for example, by using acoordinate transformation process. One registration process may includethe point-based registration technique described in U.S. Pat. No.8,010,180, filed Feb. 21, 2006, titled “Haptic Guidance System andMethod,” and incorporated by reference herein in its entirety. Onceregistered, the patient's anatomy can be tracked by the navigationsystem 22 during the procedure, and the computer system 46 maycontinuously update the virtual representations on one or both of themonitors 26, 44 in correspondence with movement of the patient.Registration of the patient's anatomy therefore allows for accuratenavigation during the surgical procedure and enables, as describedfurther below, the virtual boundaries to correspond to workingboundaries in physical space.

The surgical system 10 may guide a user during a surgical procedure byusing a surgical plan having virtual boundaries. Virtual boundariesexist in virtual space, but they may represent (i.e., correspond to)planned constraints or boundaries on movement of the tool attachment 20in physical space (i.e., they may represent “working boundaries” inphysical space). For example, in various embodiments, virtual boundariesmay represent desired tool pathways, desired limits or boundaries ontool movement, desired bone modifications (e.g., cuts), or desiredvolumes of bone to be removed. Virtual boundaries may be lines, planes,curved surfaces, volumes, or boundaries of a volume. Virtual boundariescan take any shape or form to facilitate guidance of the tool attachment20. Although the term virtual volume is used in the examples below, theterm virtual boundary refers to a virtual volume itself or to a portionof a virtual volume (e.g., a boundary of a volume).

FIG. 7 illustrates a superior view of a first virtual volume 96superimposed on a virtual bone 98. FIG. 7 also shows a virtual toolattachment 114, which represents physical tool attachment 20 (in FIGS. 7and 8, tool attachment 20 may be a planar tool 48). The image may bedisplayed intra-operatively on monitor 44 or monitor 26. In thisexample, first virtual volume 96 may have a trapezoidal top surface,although the surfaces of the virtual volume 96 may be any shape andsize. The virtual bone 98 may represent a tibia, although in othersurgical plans the virtual bone 98 may represent a femur, an acetabulum,a bone of the ankle, shoulder, spine, or arm, or any other bone. Forreference, FIG. 12 depicts an anterior view of first virtual volume 96and a second virtual volume 100.

First virtual volume 96 may represent (i.e., correspond to) boundariesconstraining tool attachment 20 (in this example, planar tool 48represented by virtual tool 114). For example, several boundaries orouter surfaces of first virtual volume 96 may represent constraints ontool attachment 20. First virtual volume 96 may include an anteriorboundary 108, a medial boundary 102, a posterior boundary 106, a lateralboundary 104, an inferior boundary 110 (see FIG. 12), and a superiorboundary 112. Each of the boundaries may be “active” or “inactive” atdifferent times during a surgical procedure. An active boundary mayrepresent a constraint in physical space (e.g., a surface thatconstrains tool attachment 20), while an inactive boundary may allowtool attachment 20 to cross. In the embodiment shown in FIG. 7, anteriorsurface 108 may be inactive, meaning the corresponding working boundaryin physical space would not constrain the tool attachment 20. Incontrast, boundaries 102, 106, 104, 110, and 112 may be active, meaningtheir corresponding working boundaries in physical space may constraintool attachment 20 and prevent substantial movement past the boundaries.

In an additional or alternative embodiment, first virtual volume 96 mayrepresent (i.e., correspond to) a volume of bone to be removed. In oneexample, the portion of virtual volume 96 that intersects the virtualbone 98, depicted as region 116 in FIG. 7, represents a volume of boneto be removed during the surgical procedure. In one embodiment, theouter boundaries of the region 116, the volume of bone to be removed,may be represented by portions of inferior boundary 110, lateralboundary 104, and the edges of the virtual bone 98 medial to the lateralboundary 104.

FIG. 8 illustrates the working boundaries that correspond to the virtualboundaries shown in FIG. 7. Working boundaries are the locations inphysical space that correspond to the virtual boundaries of the surgicalplan. Thus, based on the virtual boundaries of the surgical plan, thesurgical system 10 may constrain movement of the tool attachment 20along or past working boundaries. In this example, working boundaries208, 202, 206 (not shown), 204, 210, and 212 may correspond,respectively, to virtual boundaries 108, 102, 106, 104, 110, and 112.During a procedure, the surgical system 10 may constrain movement of thetool attachment 20 when a user attempts to move the tool attachment 20past any of the active working boundaries. In one embodiment, workingboundaries 202, 206, 204, 210, and 212 may be active during a portion ofthe procedure. Thus, although tool attachment 20 may be permitted topass inactive working boundary 208 to cut bone, the tool attachment 20would not be permitted to pass the other working boundaries. In thismanner, the surgical system 10 helps control removal of bone and othertissue according to the surgical plan.

FIGS. 9 and 10 illustrate another embodiment of a set of virtualboundaries (FIG. 9) and corresponding working boundaries (FIG. 10) thatmay be used to constrain movement of tool attachment 20 during asurgical procedure. Referring to FIG. 9, a second virtual volume 100 maybe superimposed on a virtual bone 98. The second virtual volume 100 maybe employed to constrain tool movement before, during, or simultaneouslywith the first virtual volume 96. Second virtual volume 100 may havemany of the same characteristics as first virtual volume 96. However, inone embodiment, second virtual volume 100 may have a different shape anddifferent placement relative to virtual bone 98. For example, secondvirtual volume 100 may have an irregularly-shaped top surface, as can beseen in FIG. 9, although the second virtual volume 100 may have surfacesof any shape and size.

Similar to first virtual volume 96, second virtual volume 100 mayrepresent (i.e., correspond to) boundaries in physical space that mayimpose constraints on movement of tool attachment 20 (burr 50 in FIGS. 9and 10). Second virtual volume 100 may include an anterior boundary 128,a medial boundary 122, a posterior boundary 126, a lateral boundary 124,an inferior boundary 130 (FIG. 12), and a superior boundary 132. Atdifferent times during the procedure, each of these boundaries may beactive or inactive. In one embodiment, anterior boundary 128 is inactiveto allow tool attachment 20 to cross the corresponding working boundary.

Again similar to first virtual volume 96, second virtual volume 100 mayrepresent (i.e., correspond to) a volume of bone to be removed. As shownin FIG. 9, a region 136 of virtual volume 100 may overlap with virtualbone 98. The region 136 representing bone to be removed may be definedby all or portions of inferior boundary 130 (see FIG. 12), lateralboundary 124, medial boundary 122, the superior surface of virtual bone98, the anterior surface of virtual bone 98, and the posterior surfaceof virtual bone 98. Each of the virtual boundaries of second virtualvolume 100 may correspond to working boundaries, described furtherbelow. Similarly, the exterior surfaces of virtual bone 98 correspond toexterior surfaces of a physical bone, such as tibia 6. Accordingly, theboundaries of the volume of bone to be removed are represented byvirtual boundaries/virtual bone in virtual space and workingboundaries/bone in physical space.

FIG. 10 illustrates the working boundaries that correspond to thevirtual boundaries of second virtual volume 100 shown in FIG. 9. Workingboundaries 228, 222, 226 (not shown), 224, 230, and 232 correspond tovirtual boundaries 128, 122, 126, 124, 130 and 132, respectively.Similar to the embodiment of FIGS. 7 and 8, the working boundaries maydefine boundaries across which the tool attachment 20 (burr 50 in FIGS.9 and 10) is constrained from crossing. The working boundaries may beactive or passive in any combination during a surgical procedure. In oneembodiment, one portion of a procedure, all working boundaries exceptanterior working boundary 228 are active. Working boundary 228 mayremain inactive during the procedure to permit the tool attachment 20 tocross working boundary 228 and modify bone.

FIG. 11 illustrates an anterior view of the first virtual volume 96 andthe second virtual volume 100 superimposed onto a virtual tibia 98. Inone embodiment, the first virtual volume 96 and the second virtualvolume 100 may be used/activated at different times during a surgicalprocedure to guide a tool attachment 20. Thus, the virtual volumes 96,100 may each create corresponding working boundaries during differentportions of the procedure.

The two virtual volumes 96, 100 are shown together in FIG. 11 toillustrate their relationship to each other. The second virtual volume100 may be offset in the medial-lateral direction from the first virtualvolume 96. In the embodiment of FIG. 11, the second virtual volume 100may be offset in the lateral direction, although the direction mightchange depending on the surgical procedure to be completed, or for kneerepair procedures, which knee and which condyle is being prepared toreceive an implant. For example, the lateral virtual boundary 124 of thesecond virtual volume 100 may be located in a more lateral position thanthe lateral virtual boundary 104 of the first virtual volume 96. Thesecond virtual volume 100 also may be offset from the first virtualvolume 96 in the superior-inferior direction. In the embodiment of FIG.11, the second virtual volume 100 may be offset in the superiordirection. For example, inferior virtual boundary 130 of second virtualvolume 100 may be offset in the superior direction from the inferiorvirtual boundary 110 of the first virtual volume 96. In addition oralternatively, the superior virtual boundary 132 of the second virtualvolume 100 may be offset in the superior direction from the superiorvirtual boundary 112 of the first virtual volume 96. The offset surfacesof the first and second virtual volumes 96, 100 may be substantiallyparallel to each other or may have a different angle relative to eachother. The first and second virtual volumes 96, 100 may be offset tooptimize the final configuration of the bone that is prepared during thesurgical procedure. These benefits will be explained further below inthe “Bone Preparation Method” section.

In general, to constrain movement of the tool attachment 20, thesurgical system 10 may map the virtual boundaries of the surgical plan,such as the virtual boundaries of first virtual volume 96 and secondvirtual volume 100, onto the patient's bone to create workingboundaries. As described earlier, the navigation system 22 may track thelocation of the tool attachment 20 and one or more bones 6, 8. The toolattachment 20 is represented virtually (i.e., the tool attachment 20properties and dimensions are stored in the surgical system 10), and asdescribed earlier, the patient's bones are registered with thethree-dimensional images used in the surgical plan. The tracking andregistration information allows the surgical system 10 to map thevirtual boundaries of the surgical plan onto the physical bone, such astibia 6, to create working boundaries. When the patient moves, thevirtual boundaries and therefore the working boundaries are updated.When the tool attachment 20 contacts or passes a working boundary, thesurgical system 10 (via the computer system 46) may cause forces to beapplied to the robotic arm 16. These forces may act to constrain furthermovement of the tool attachment 20.

Bone Preparation Method

Referring to FIG. 12, in an exemplary method, the surgical system 10,including the tool system 17, is used to implement a surgical plan. Thesurgical plan may include first and second virtual volumes 96, 100 andmay guide preparation of one or more of a patient's bone to receiveimplant components, such as the components of implant system 54.

In one embodiment, multiple tool attachments 20 are used during thesurgical procedure. Each tool attachment 20 can be removed from andreconnected to the distal end of the robotic arm 16 byremoving/reconnecting the tool attachments 20 to the tool body 18. Inone example, during a first portion of the procedure, a planar tool(e.g., saw 48) may be used to modify bone. During a second portion ofthe procedure, a rotary tool (e.g., burr 50 or drill 52) may be used tomodify bone. In an additional or alternative embodiment, the burr 50 maybe used during a second portion of the procedure and the drill 52 may beused during a third portion of the procedure. In yet another additionalor alternative embodiment, an oscillating saw may be used during a firstportion of a procedure, and a reciprocating saw may be used during asecond portion of a procedure. It should be understood that “firstportion,” “second portion,” and “third portion” do not necessarilydesignate order, but rather serve to distinguish between differentportions of the procedure. One or more of a planar tool, such as anoscillating or reciprocating saw, a burr 50, or a drill 52 (e.g., one,two, three, four, or more tools) may be used during a procedure, and anytools that are used during the procedure may be used in any order.Accordingly, each tool attachment 20 may be connected, removed, orreconnected to the tool body 18 and the distal end of the robotic arm 16during a surgical procedure.

A bone may be modified to include first and second surfaces. The firstand second surfaces may correspond to bone-contacting surfaces of anytype of implant. For example, the first surface may receive to abone-contacting surface of a tibial component, femoral component, orplate, and the second surface may receive another bone-contactingsurface of the tibial component, femoral component, or plate. The firstand second surfaces may be planar, curved, cylindrical, or any othershape corresponding to a surface of the implant (e.g., corresponding toa main bone-contacting surface, a peg, a keel, a screw hole, etc.).

In one embodiment, during a first portion of a surgical procedure, thefirst virtual volume 96 may be used or activated to constrain movementof a planar tool (e.g., saw 48 or any other planar tool). The firstvirtual volume 96 may therefore be superimposed onto a virtual bone 98(Step 1210). During this first portion of the procedure, the planar toolmay be used to create a first surface. The first surface may be a planarsurface on the patient's tibia 6. This planar surface may be, forexample, along working boundary 210 shown in FIG. 8 (Step 1230). As thepractitioner cuts into the tibia 6, the tool attachment 20 may beconstrained from cutting inferior to working boundary 210. The end oftool attachment 20 also may be constrained from cutting posterior toworking boundary 106. The remaining working boundaries of first virtualvolume 96 may similarly constrain movement of the planar tool attachment20.

In this manner, the first virtual volume 96 may guide the user to createa first surface that is an exposed planar surface along the patient'stibia. The planar surface may be located near a proximal end of thepatient's tibia 6 and may be oriented substantially perpendicular to alongitudinal axis through the tibia 6. This planar surface, createdalong working boundary 210, may be referred to as the “tibial floor.”The tibial floor created by the planar tool may be configured to receivea tibial component 72 implanted on (e.g., adjacent to) the tibial floor.An implant component may be adjacent to a bone when it is touching thebone or near the bone. In one embodiment, when implanted, the inferiorsurface 84 of the tibial component 72 may be in substantially continuouscontact with the tibial floor. In other embodiments, either during tibiarepair procedures or procedures on other bones, the first surface mayhave a non-planar shape and may, for example, includes curves or ridges.

During a second portion of the surgical procedure, the second virtualvolume 100 may be used or activated to constrain movement of a rotarycutting tool (e.g., burr 50 or drill 52). During this portion, thesecond virtual volume 100 may be superimposed onto virtual bone 98 (Step1220). The rotary tool may be used to create a second surface of thetibia 6. The second surface may be along lateral working boundary 224,which corresponds to lateral virtual boundary 124 (Step 1240). Lateralworking boundary 224, along with the other working boundaries of secondvirtual volume 100, may constrain the rotary tool within the bounds ofthe second virtual volume 100.

The second virtual volume 100 may therefore guide the user to create asecond surface that is an exposed surface substantially perpendicular tothe exposed planar surface created by the planar cutting tool. Theexposed surface created by the rotary cutting tool may be located near aproximal end of the patient's tibia 6 but may be oriented substantiallyparallel to a longitudinal axis through tibia 6. The surface created bythe rotary cutting tool along working boundary 224 may be referred to asthe “tibial wall.” In other embodiments, either during tibia repairprocedures or procedures on other bones, the second surface may have anyother angle relative to the first surface. In another embodiment, thesecond surface may be created with planar tool 48.

In other embodiments, when the prepared bone is a femur or other bone,the first and second virtual volumes may constrain or guide movement ofa tool along surfaces of the femur or other bone. Similar to repairs ofthe tibia, during bone repair procedures of the femur or any other bone,the first and second virtual volumes may correspond to workingboundaries and may facilitate robotic modifications to create first andsecond surfaces that are desired and suitable for the specific bonerepair procedure. The first and second surfaces may be perpendicular toeach other or may have another angle relative to each other. The methodsdescribed herein may be implemented on an area of a bone that forms ajoint (e.g., on an articular surface) or on a portion of a bone outsideof a joint (e.g., the shaft of a long bone).

The positioning of the first virtual volume 96 with respect to thesecond virtual volume 100 may help ensure that, after implantation, theinferior surface 84 of tibial implant component 72 is in continuouscontact with the tibial floor. The tibial floor may be considered thesurface along working boundary 220 created by the planar tool, asdescribed above, plus any “extension” of the tibial floor created by therotary tool. The extension of the tibial floor can be seen in FIG. 11 asthe portion of virtual boundary 130 (of the second virtual volume 100)that protrudes in a lateral direction from the lateral boundary 104 (ofthe first virtual volume 96). Once both the planar tool and the rotarytool have been used to sculpt the tibial floor in this area, theprepared tibial floor of the patient may have a similar surface. Inother words, the tibial floor of the prepared bone may have a planarsurface along working boundary 220 (of the first virtual volume 96), aslight step, and then a shorter planar surface along working boundary230 (of second virtual volume 100). This step in the bone may beflattened when implant component 72 is implanted onto the preparedsurfaces of the tibia 6, ensuring a snug fit between the component 72and the prepared tibial floor. In other embodiments, the structuraldifferences between the planar tool and the rotary tool will cause thefinal tibial floor to be smooth, without a step, even when the inferiorboundary 130 of the second virtual volume 100 is offset in a superiordirection from the inferior boundary 110 of the first virtual volume 96.

The offset of the second virtual volume 100 relative to the firstvirtual volume 96 may minimize the stress riser at the junction betweenthe first and second surfaces. For example, during a bone repairprocedure of a tibia, if an indentation were created between the tibialfloor and the tibial wall, there might be a larger stress riser at thejunction of the bone surfaces than if no indentation were created. Theoffset between the first and second virtual volumes helps to ensure thatthe junction between the bone surfaces includes a step or is continuous,rather than including an indentation.

In an additional or alternative embodiment, a third portion of thesurgical procedure may include using drill 52 to drill one or moreindentations (e.g., channels, holes) in tibia 6 or femur 8. For example,one or more indentations in tibia 6 may be drilled to receive keels 86or 88. Similarly, one or more indentations in femur 8 may be drilled toreceive posts 66, 68. A third virtual volume may guide drill 52 duringcreation of indentations by, for example, constraining movement of drill52 past working boundaries corresponding to the third virtual volume.

During the surgical procedure, various tools may be interchanged andalternately coupled to tool body 18. This allows a variety of types ofbone modifications to be made during a single surgical procedure. Inaddition, use of various tools allows the bone to be accurately sculptedto receive implant components having different configurations ofbone-contacting surfaces. The use of various tools also allows for theeffective use of the different cutting characteristics of differenttools to form the bone-contacting surfaces. In one embodiment, the bonemay be prepared with multiple tools to receive a press-fit implantcomponent. For example, creating a planar tibial floor with a planartool, a tibial wall with a burr, and indentations with a drill mayprepare the tibia 6 to receive a press-fit tibial implant component 72such that bone ingrowth will securely fix the implant component 72 tothe tibia 6.

In one embodiment, surfaces of the tibia may be prepared to receive thefirst side wall 78 and second side wall 80 of tibial component 72. Thebone surfaces may be prepared such that they will surround the outersurfaces of the tibial component 72 and hold the component in apress-fit manner. In some embodiments, to securely hold the implantedcomponent, the prepared bone surfaces may surround an area that isslightly smaller than the tibial component 72. In another embodiment,the bone may be prepared with multiple tools to receive a cementedimplant component or an implant component secured to the bone by anyother fixation method. FIG. 13 illustrates tibial component 72 placedagainst the tibia 6 after the tibia 6 has been prepared as describedherein (see Step 1250 of FIG. 12).

The surfaces of a femur may be prepared in accordance with the methodsdescribed herein to receive a femoral component 56 (see FIG. 5), whichmay be press-fit or cemented. For example, the bone surfacecorresponding to planar surface 64 may be a first surface prepared witha first virtual boundary and a planar tool, and other bone surfaces maybe prepared with a second virtual boundary and a rotary tool and maycorrespond to and receive other bone-contacting surfaces of the femoralcomponent 56. In one embodiment, the femoral surfaces may be prepared todirectly match the bone-contacting surfaces of the femoral component.However, in another embodiment, the femoral surfaces may be prepared topartially deviate from the bone-contacting surfaces of the femoralcomponent to ensure that the femoral component 56 is securely held bythe bone.

To facilitate a secure press-fit, the bone surface corresponding toplanar surface 64 and the bone surface corresponding to second post 68may be prepared such that the bone between the planar surface 64 andsecond post 68 of the implanted component will be “squeezed,” and thepressure will help hold the component 56 in place. Similarly, thesurfaces corresponding to first post 66 and second post 68 may beprepared farther apart than the distance between the posts 66, 68 suchthat the bone between the implanted posts will be squeezed by theimplanted posts. In yet another embodiment, the holes to receive posts66, 68 may be prepared to be smaller than the posts themselves such thatthe posts are squeezed within their holes. The ability to use multipletools during the surgical procedure, as well as the precise cuts allowedby the planar tool, may enhance a user's ability to prepare bone toreceive a press-fit femoral component 56 or any other type implantcomponent, whether or not the implant is secured to the bone bypress-fit or by another method.

To facilitate a stable fit to the bone when an implant is secured to thebone with or without cement, the femoral surfaces may be prepared withenough deviation from the bone-contacting surfaces of the femoralcomponent 56 such that errors in the execution of the bone modificationsare biased to certain regions. For example, bone modifications may beexecuted to ensure that there is substantially continuous bone contactbetween planar surface 64 and the femur and between an anterior portionof curved surface 61 and the femur, leaving a region of diminished bonecontact between the distal portion of the curved surface 61 and thefemur. The amount of bone contact between two surfaces, such as the boneand a bone-facing implant surface, may be quantified by pressure betweenthe two surfaces, by the percentage of the bone-facing implant surfacethat is touching the bone, or by any other method of measuring contactbetween two surfaces. The primary contact between the femoral component56 and the bone in the anterior and posterior regions may ensure thatthe implant will rest stably on the bone, even if such primary contactcauses diminished bone contact along portions of curved surface 61.

In one embodiment of a surgical procedure, a planar tool may be used toprepare bone surfaces to receive and/or contact the following featuresor surfaces of implant components: a) inferior surface 84 of tibialcomponent 72, and b) the planar surface 64 of femoral component 56. Arotary tool may be used to prepare bone surfaces to receive and/orcontact the following features or surfaces: a) side wall 78 of tibialcomponent 72, b) curved surface 61 of femoral component 56; c) firstpost 66 and second post 68 of femoral component 56; and d) thebone-contacting surface and posts of a patello-femoral component, ifbeing used.

In another embodiment, the planar tool may be used to prepare bonesurfaces to receive and/or contact the following features or surfaces ofimplant components: a) inferior surface 84 of tibial component 72, andb) the planar surface 64 of femoral component 56. A first rotary tool,such as a burr, may be used to prepare bone surfaces to receive and/orcontact the following features or surfaces: a) the side wall 78 oftibial component 72, b) the rim of aperture 94 of tibial component 72,and c) the curved surface 61 of femoral component 56. A second rotarytool, such as a drill, may be used to prepare bone surfaces to receiveand/or contact the following features or surfaces: a) the first post 66and second post 68 of femoral component 56; and b) the keels 86, 88 oftibial component 72.

While principles of the present disclosure are described herein withreference to illustrative embodiments for particular applications, itshould be understood that the disclosure is not limited thereto. Thosehaving ordinary skill in the art and access to the teachings providedherein will recognize additional modifications, applications,embodiments, and substitution of equivalents all fall within the scopeof the embodiments described herein. Accordingly, the invention is notto be considered as limited by the foregoing description.

We claim:
 1. A computer system for controlling a medical robotic systemfor preparing a bone of a patient, wherein the medical robotic systemincludes a power tool with planar and rotary attachments, the computersystem comprising: an electronic storage device storing instructions forcontrolling the medical robotic system; and a processor configured toexecute the instructions to: determine a first virtual boundary for theplanar attachment based on received patient parameters; determine asecond virtual boundary for the rotary attachment based on the receivedpatient parameters; constrain motion of the planar attachment based onthe first virtual boundary; and constrain motion of the rotaryattachment based on the second virtual boundary.
 2. The computer systemof claim 1, wherein the processor is further configured to executeinstructions to position and align, in six degrees of freedom, at leastone of the planar attachment or the rotary attachment.
 3. The computersystem of claim 1, wherein constraining motion of the planar attachmentincludes constraining motion of the planar attachment along a firstworking boundary to create a first surface of the bone, wherein thefirst working boundary corresponds to the first virtual boundary.
 4. Thecomputer system of claim 1, wherein the processor is further configuredto execute instructions to: determine a third virtual boundary for athird attachment based on the received patient parameters, wherein thethird attachment is different than the rotary attachment and the planarattachment; and constrain motion of the third attachment based on thethird virtual boundary.
 5. The computer system of claim 1, wherein thebone is a tibia.
 6. The computer system of claim 1, wherein the firstvirtual boundary is configured to guide a robotic arm to cut the bonewith the planar attachment to create a first surface.
 7. The computersystem of claim 6, wherein the second virtual boundary is configured toguide a robotic arm to cut the bone with the rotary attachment to createa second surface.
 8. A computer system for controlling a medical roboticsystem for preparing a bone of a patient, comprising: an electronicstorage device storing instructions for controlling the medical roboticsystem; and a processor configured to execute the instructions to:determine a first virtual volume for a first tool based on receivedpatient parameters, wherein the first virtual volume includes a firstsurface; determine a second virtual volume for a second tool based onthe received patient parameters, wherein the first tool is differentthan the second tool, wherein the second virtual volume includes asecond surface, and wherein the second surface is offset from the firstsurface; and constrain motion of the medical robotic system based on thefirst virtual volume and the second virtual volume; wherein the firsttool and the second tool are attached to the same power tool mounted onan end of a robot arm.
 9. The computer system of claim 8, wherein thefirst surface and the second surface correspond to bone contactingsurfaces of an implant.
 10. The computer system of claim 8, wherein thefirst surface is configured to receive a tibial component, a femoralcomponent, or a plate of an implant; and wherein the second surface isconfigured to receive a tibial component, a femoral component, or aplate of an implant.
 11. The computer system of claim 8, wherein thefirst surface and the second surface are planar surfaces.
 12. Thecomputer system of claim 8, wherein the first tool is a planar tool andthe second tool is a rotary tool.
 13. The computer system of claim 12,wherein the processor is further configured to execute instructions to:determine a third virtual volume for a third tool based on the receivedpatient parameters, wherein the third tool is a drill; and constrainmotion of the third tool based on the third virtual boundary.
 14. Thecomputer system of claim 12, wherein the planar tool is a saw, therotary tool is a burr, and the saw and the burr are adapted tointerchangeably connect to the end of the robotic arm.
 15. The computersystem of claim 8, wherein the first surface and the second surface areconfigured to receive a press-fit implant.
 16. The computer system ofclaim 8, wherein the bone is a tibia, the first surface is a tibialfloor, and the second surface is a tibial wall.
 17. A computer systemfor controlling a medical robotic system for preparing a bone of apatient, comprising: an electronic storage device storing instructionsfor controlling the medical robotic system; and a processor configuredto execute the instructions to: determine a first virtual volume for afirst tool based on received patient parameters, wherein the first toolis an oscillating planar tool; determine a second virtual volume for asecond tool based on the received patient parameters, wherein the secondtool is a reciprocating planar tool; and constrain motion of the firsttool based on the first virtual volume; and constrain motion of thesecond tool based on the second virtual volume; wherein the first tooland the second tool are attached to the same power tool mounted on anend of a robot arm.
 18. The computer system of claim 17, wherein theprocessor is further configured to execute instructions to position andalign, in six degrees of freedom, at least one of the first tool or thesecond tool.
 19. The computer system of claim 17, wherein constrainingmotion of the first tool includes constraining motion of the first toolalong a first working boundary to create a first surface of the bone,wherein the first working boundary corresponds to the first virtualboundary of the first virtual volume.
 20. The computer system of claim17, wherein the processor is further configured to execute instructionsto: determine a third virtual volume for a third tool based on thereceived patient parameters, wherein the third tool is different thanthe first tool and the second tool; and constrain motion of the thirdtool based on the third virtual volume.